Small, high-capacity, and cylindrical lithium primary batteries, and various types of rechargeable batteries have been used as a drive power supply for portable electric devices such as a camera. A higher voltage and a higher capacity are required for these batteries as the portable electric devices have higher performance and more sophisticated functions. To satisfy these requirements, batteries constituted by a spiral electrode group formed by winding laminated positive electrode plate, negative electrode plate, and separator interposed therebetween into a spiral shape are widely and generally used. For securing high performance and uniform quality as well as increasing productivity of the spiral electrode group for the various types of cylindrical batteries, it is important to wind the electrode plates and the separator in a spiral shape while eliminating a winding displacement between the positive and negative electrode plates and the separator, preventing an elongated state caused by an abnormally strong tensile force applied on the electrode plates and the separator, and avoiding slack of the electrode plates and the separator.
In view of the foregoing, the present applicant previously proposed an apparatus for manufacturing a spiral electrode group with the high performance and the uniform quality described above (see Japanese Patent Laid-Open Publication No. Hei. 09-147878). In this manufacturing apparatus, a belt-shape separator is divided into a first region on one side and a second region on the other side at the center. The first region is held between positive and negative electrode plates. A winding shaft engaged at a boundary between both the regions folds the separator into two so as to wind the electrode plates and the separator into a spiral shape while the first and second regions are respectively sucked by first and second suction means. Thus, the spiral electrode group is manufactured while feeding means are moving the first and second regions sucked and held by individual endless belts of the first and second suction means toward the winding shaft from the both sides, thereby preventing an excessive tensile force from being applied to the separator and the like constituting the spiral electrode group, and simultaneously rotational feeding speeds of the endless belts are being controlled so as to optimize the tensile force, thereby enabling to manufacture a spiral electrode group while preventing a generation of elongation of the separator and the like, and a generation of displaced winding between the positive and negative electrode plates.
When this apparatus for manufacturing a spiral electrode group is used for manufacturing a spiral electrode group for a nickel-cadmium battery or a nickel-metal hydride battery, since positive and negative electrode plates have relatively large tensile strength, and high resistance against a tensile force applied in winding, and separator, which tends to undergo the influence from the tensile force most, has a certain degree of resistance against and recoverability from elongation in both of these types of batteries, a relatively excellent spiral electrode group can be obtained. However, when a spiral electrode group for a cylindrical lithium primary battery and the like is manufactured, since a lithium metal foil tape in a belt shape constituting a negative electrode plate has extremely small resistance against a tensile force, the tape tends to generate a plastic deformation, thereby being elongated by a slight tensile force, resulting in a change in the shape and the dimension of the spiral electrode group. Thus, a battery using this spiral electrode group generates a decrease and a variation of battery characteristics.
On the other hand, the lithium metal foil tape may be wound while a tensile force is hardly applied to the tape. However, since the belt-shape lithium metal foil tape has a very soft surface, and thus the tape tends to present a plastic deformation, when the tape is pressed to or slid on the surface of the metal in a contact state, the tape tends to adhere to the surface of various types of metal. Thus, the constitution of the manufacturing apparatus described above cannot securely wind a thin belt-shape lithium metal foil tape without applying a tensile force, and generating slack. As a result, since a manufactured spiral electrode group is very loosely wound as an electrode group, the electrode group is so unstable to present a change in the shape and the dimension, thereby causing a tendency of a displacement in the winding. Thus, the present applicant previously proposed an apparatus for manufacturing a spiral electrode group which winds constituting materials while automatically adjusting the feeding speed variably to an optimal one which does not apply an unnecessarily high tensile force according to a variation in thickness of the materials such as electrode plates (Japanese Patent Laid-Open Publication No. Hei. 11-336349). In this manufacturing apparatus, as shown in a schematic front view in FIG. 11, a rotation table 1 including three winding cores 2 provided on the outer periphery at an interval of 120° rotates by an intermittent increment of 120° in a direction indicated by an arrow in the drawing, thereby sequentially moving the three winding cores 2 for positioning to a winding position P where the winding core 2 comes in contact with a tape suction drum 3. The winding core 2 is rotationally driven at the winding position P to wind a negative electrode plate 4, a separator 7, and a positive electrode plate 8 in a spiral shape while receiving the negative electrode plate 4 from the tape suction drum 3, thereby manufacturing a spiral electrode group 9.
Linear guides 10 are respectively provided between the individual neighboring two winding cores 2 of the three winding cores 2. A guiding chuck member 11 and a positioning chuck member (not shown) are respectively provided so as to smoothly slide with almost no slide load received on the individual guides 10. The guiding chuck member 11 chucks an end of the separator 7 so as to pass through an engagement slit (not shown) in the winding core 2. The positioning chuck member chucks an end of the positive electrode plate 8 while the positive electrode plate 8 is laminated on, and positioned with respect to the separator 7, and then feeds the positive electrode plate 8 in a predetermined positioned state with respect to the negative electrode plate 4 to the winding core 2 while the positioning chuck member is sliding on the guide 10 as the separator 7 being wound on the winding core 2 is transported. When the winding core 2 rotates for winding, the guiding chuck member 11 on the left side with respect to the winding core 2 in the drawing moves upward along the guide 10 as the winding core 2 rotates for winding, thereby serving for the winding core 2 as a weight for applying a proper tensile force to the separator 7. Similarly, the guiding chuck member 11 on the right side with respect to the winding core 2 in the drawing serves for the winding core 2 as a weight for applying a proper tensile force to the positive electrode plate 8.
On the other hand, the plurality of tape suction drums 3 are provided at an equal interval on an outer periphery of a transporting rotation drum (not shown), and are not connected with a rotationally driving source, but are rotatably supported by rotation support shaft 12. Simultaneously, an extremely weak braking force as large as preventing a continuous rotation by an inertia force is applied to the tape suction drums 3. The negative electrode plate 4, which is formed as a thin belt-shape lithium metal foil tape, and is cut into a predetermined length required for constituting the one spiral electrode group 9, is sucked and held on the outer peripheral surface of the tape suction drum 3 in advance in a wound state. Simultaneously, the tape suction drums 3 are sequentially transported to the winding position P by an intermittent rotation of the transporting rotation drum, and then is pressed against the winding core 2 with a proper force by a drum support lever 14 rotated and urged by a helical spring 13 toward a direction indicated by an arrow in the drawing.
In this manufacturing apparatus, when the winding core 2 rotates, the tape suction drum 3 in contact with the winding core 2 is rotated together in synchronism with the winding core 2 only by a friction force generated by the contact with the winding core 2. As a result of the rotation, the negative electrode plate 4 sucked and held on the outer peripheral surface of the tape suction drum 3 is wound together with portions of the separator 7. Thus, since a tensile force is hardly applied to the negative electrode plate 4 sucked and held on the tape suction drum 3 supported rotatably, though the negative electrode plate 4 is a thin lithium metal foil tape, it is not elongated. Also,- since the tape suction drum 3 rotates through the drum support lever 14 as the diameter of the spiral electrode group 9 changes, the rotation speed of the tape suction drum 3 automatically increases so as to be always variably adjusted to a stable optimal value as the diameter of the spiral electrode group 9 increases though the winding core 2 always rotates at a constant speed. As a result, since a tensile force is hardly applied to the negative electrode plate 4 in the winding process for the spiral electrode group 9, the negative electrode plate 4 is not elongated.
In the manufacturing apparatus described above, the tape suction drum 3 rotatably supported is rotated together in synchronism with the winding core 2 by the friction force acting between the negative electrode plate 4 sucked and held on the outer peripheral surface of the tape suction drum 3 and the outer peripheral surface of the winding core 2 or the separator 7, though the negative electrode plate 4 is a thin lithium metal foil tape, it is not elongated. Thus, the spiral electrode group 9 with a required shape is surely manufactured. However, this manufacturing apparatus is not proper for mass-producing the spiral electrode group 9 at high productivity.
Namely, in this manufacturing apparatus, the negative electrode plate 4 is cut into a predetermined dimension after a positioning tape and a negative electrode lead are attached at a negative electrode plate supplying part (not shown) additionally provided for this apparatus, the separator 7 is cut into a predetermined dimension at a separator supplying part additionally provided for the apparatus, and the positive electrode plate 8 is cut into a predetermined dimension after a positive electrode lead is attached at a positive electrode plate supply part additionally provided for the apparatus. Then, after the negative electrode plate 4, the separator 7, and the positive electrode plate 8 are supplied so as to have required relative positions with respect to the winding core 2 transported to the single winding position P, the winding is conducted at this winding position P. In this way, in this manufacturing apparatus, the individual constituting materials for the spiral electrode group 9 are supplied at the single winding position P so as to be assembled at the predetermined relative positions after these materials are made into the predetermined shapes at the individual supplying parts additionally provided for this apparatus, and then these materials are wound into the spiral shape. Thus, it is not possible to supply the positive electrode plate 8, the negative electrode plate 4, and the separator 7 until a next winding core 2 is transported to the winding position P after one spiral electrode group 9 has been manufactured at the winding position P. Thus, the increase of the productivity is limited.
In addition, this manufacturing apparatus is constituted such that the negative electrode plate 4 with a predetermined length required for constituting one spiral electrode group 9 is maintained in the wound state on the tape suction drum 3 while the entire part in the lengthwise direction is vacuum-sucked. Simultaneously the separator 7 is wound by the winding core 2 while the proper tensile force is applied to the separator 7 by slidingly moving the guiding chuck members 11 along the guides 10 after the both ends of the separator 7 with a predetermined length for constituting one spiral electrode group 9 are chucked by the guiding chuck members 11. Thus, in this manufacturing apparatus, since it is necessary to use the tape suction drum 3 with a diameter corresponding to the length of the negative electrode plate 4, and the guides 10 with a length corresponding to the length of the separator 7, the apparatus should be a dedicated apparatus for manufacturing a spiral electrode group 9 for a specific battery. Consequently, it is necessary to individually prepare the apparatuses for the different types of spiral electrode groups different in length and width of the positive electrode plate 8, the negative electrode plate 4, and the separator 7, resulting in increasing the cost.
The present invention is devised in light of the foregoing, and an object of the invention is to provide a manufacturing method and a manufacturing apparatus for highly precisely and highly productively manufacturing various spiral electrode groups different in length and width of the positive and negative electrode plates and the separator on a single apparatus.